Display device and driving method thereof

Abstract

A display device includes: a plurality of pixels that represent a first color, a second color, a third color, and white; a signal processor that converts input image signals respective to the colors into output image signals respective to the colors plus an output image signal for the white color, calculates a current consumption amount consumed in the pixels based on the output image signals, and compensates the output image signals in accordance with the current consumption amount; and a data driver that converts the output image signals into data voltages and supplies the data voltages to the pixels.

1 . A display device comprising:
 a plurality of pixels that represent a first color, a second color, a third color, and white;   a signal processor that converts input image signals (referred to as first, second, and third input image signals) respective to first, second, and third colors into output image signals (referred to as first, second, and third output image signals) respective to the first, second, and third colors plus an output image signal (referred to as a white output image signal) for the white color, calculates a current consumption amount consumed in the pixels based on the first, second, third, and white output image signals, and compensates the first, second, third, and white output image signals in accordance with the current consumption amount; and   a data driver that converts the white output image signal and the first to third output image signals into data voltages and supplies the data voltages to the pixels.   
   
   
       2 . The display device of  claim 1 , wherein:
 the signal processor comprises:
 a scaling unit that changes a magnitude of the first, second, and third input image signals based on a current change constant to generate first, second, and third conversion image signals; 
 an RGBW converter that generates the first, second, third, and white output image signals from the first, second, and third conversion image signals based on a luminance compensation constant; and 
 a constant determiner that defines the current change constant from the current consumption amount and defines the luminance compensation constant from the current consumption amount and a total number defined by counting luminances of the first, second, third, and white output image signals exceeding a threshold in one frame. 
   
   
   
       3 . The display device of  claim 2 , wherein the constant determiner determines whether the current consumption amount is within a predetermined range, and, when the current consumption amount is within the predetermined range, outputs a previous current change constant and a previous luminance compensation constant as a new current change constant and a new luminance compensation constant, and, when the current consumption amount is out of the predetermined range, changes at least one of the previous current change constant and the previous luminance compensation constant to output such as the new current change constant and the new luminance compensation constant. 
   
   
       4 . The display device of  claim 3 , wherein the predetermined range of the current consumption amount is about 10% to about 35% of a maximum current amount. 
   
   
       5 . The display device of  claim 4 , wherein the predetermined range of the current consumption amount is about 15% to about 30% of a maximum current amount. 
   
   
       6 . The display device of  claim 2 , wherein the RGBW converter generates the white output image signal and the first, second, and third output image signals based on the first, second, and third input image signals and the luminance compensation constant. 
   
   
       7 . The display device of  claim 6 , wherein the RGBW converter comprises:
 a gamma converter that gamma-converts the generated first, second, and third input image signals to generate first, second, and third luminance signals, respectively;   a calculator that generates a white luminance signal using the luminance compensation constant and the first, second, and third luminance signals, and converts the first, second, and third luminance signals into first, second, and third compensation luminance signals L 1 ′, L 2 ′, and L 3 ′, respectively;   a clipping unit that respectively compares the first, second, and third compensation luminance signals and the threshold luminance, and changes the first, second, and third compensation luminance signals having a luminance exceeding the threshold luminance into first, second, and third output luminance signals, wherein luminances of the first, second, and third output luminance signals are defined to be the threshold luminance;   a three color de-gamma converter that converts the first, second, and third output luminance signals into first, second, and third output gray signals; and   a white de-gamma converter that converts the white luminance signal into the white output image signal.   
   
   
       8 . The display device of  claim 7 , wherein the RGBW converter further comprises:
 a first signal ordering unit that arranges the first, second, and third input image signals in order of magnitude of the grays of the respective first, second, and third input image signals; and   a second signal ordering unit that is formed between the clipping unit and the three color de-gamma converter and rearranges the first, second, and third input image signals in accordance with color.   
   
   
       9 . A driving method of a display device, the method comprising:
 receiving input image signals of three colors;   converting the input image signals into four-color output image signals;   calculating a current consumption amount consumed in pixels using the output image signals;   defining a current change constant from the current consumption amount, and   determining the luminance compensation constant from the current consumption amount and the total number of luminances exceeding a threshold luminance in the first, second, third, and white output image signals of one frame;   changing magnitudes of the input image signals based on the current change constant to generate conversion image signals; and   generating the output image signals from the conversion image signals based on the luminance compensation constant.   
   
   
       10 . The driving method of  claim 9 , wherein the calculation of the current consumption amount comprises receiving the output image signals for first, second, third, and white colors and calculating the current consumption amount. 
   
   
       11 . The driving method of  claim 10 , wherein the determination of the current change constant and the luminance compensation constant comprises:
 determining whether the current consumption amount is included within a predetermined range;   when the current consumption amount is included in the predetermined range, outputting a previous current change constant and a previous luminance compensation constant as a new current change constant and a new luminance compensation constant;   when the current consumption amount is less than a lower limit of the predetermined range, determining that the current change constant has a maximum value;   when the current change constant has the maximum value, defining a current luminance compensation constant by using an operation, and when the current change constant does not have the maximum value, increasing the current change constant by a compensation value ΔS to calculate a new current change constant;   when the current consumption amount is larger than or equal to the lower limit of the predetermined range, determining that the luminance compensation constant has a minimum value;   when the luminance compensation constant has the minimum value, decreasing the current change constant by the compensation value ΔS to calculate a new current change constant, and   when the luminance compensation constant does not have the minimum value, decreasing the luminance compensation constant by the compensation value ΔC to calculate a new luminance compensation constant.   
   
   
       12 . The driving method of  claim 11 , wherein the predetermined range of the current consumption amount is about 10% to about 35% of a maximum current amount. 
   
   
       13 . The driving method of  claim 12 , the luminance compensation constant is defined based on the total number. 
   
   
       14 . The driving method of  claim 12 , wherein the respective compensation values ΔS and ΔC are fixed or varied. 
   
   
       15 . The driving method of  claim 14 , wherein the respective compensation values ΔS and ΔC are fixed based on the number of bits of the output image signals. 
   
   
       16 . The driving method of  claim 15 , wherein the respective compensation values ΔS and ΔC have a value of 2 the number of bits in the output image signals). 
   
   
       17 . The driving method of  claim 9 , wherein the current change constant has an initial value of “1”, and the luminance compensation constant has an initial value of “0”.